netdev - [PATCH net 2/2] netfilter: conntrack: clamp maximum hashtable size to INT

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Message-Id: <20250109123806.42021-2-pablo@netfilter.org>
Date: Thu,  9 Jan 2025 13:38:06 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de
Subject: [PATCH net 2/2] netfilter: conntrack: clamp maximum hashtable size to INT_MAX

Use INT_MAX as maximum size for the conntrack hashtable. Otherwise, it
is possible to hit WARN_ON_ONCE in __kvmalloc_node_noprof() when
resizing hashtable because __GFP_NOWARN is unset. See:

  0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")

Note: hashtable resize is only possible from init_netns.

Fixes: 9cc1c73ad666 ("netfilter: conntrack: avoid integer overflow when resizing")
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_conntrack_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 9db3e2b0b1c3..456446d7af20 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2517,12 +2517,15 @@ void *nf_ct_alloc_hashtable(unsigned int *sizep, int nulls)
 	struct hlist_nulls_head *hash;
 	unsigned int nr_slots, i;
 
-	if (*sizep > (UINT_MAX / sizeof(struct hlist_nulls_head)))
+	if (*sizep > (INT_MAX / sizeof(struct hlist_nulls_head)))
 		return NULL;
 
 	BUILD_BUG_ON(sizeof(struct hlist_nulls_head) != sizeof(struct hlist_head));
 	nr_slots = *sizep = roundup(*sizep, PAGE_SIZE / sizeof(struct hlist_nulls_head));
 
+	if (nr_slots > (INT_MAX / sizeof(struct hlist_nulls_head)))
+		return NULL;
+
 	hash = kvcalloc(nr_slots, sizeof(struct hlist_nulls_head), GFP_KERNEL);
 
 	if (hash && nulls)
-- 
2.30.2